Developer for photographic plates, films, papers, and the like



Patented Feb. is, 1927.

- UNITED, STATES PATENT orrics.

KARL BINDER, OF STUTTGART, GERMANY.

DEVELOPER FOR PHOTOGRAIBHIG PLATES, FILMS, PAPERS, AND THE LIKE.

No Drawing. Application filed August 25, 1925, S erlal No 52,459, and in Great Britain July 14,1925.

The present invention relates to a process for the manufacture of developers for photographic plates and the like.

The object of the invention is to provide 'firstly, as is well known, the chemically .ac-'

tive rays from acting on the light sensitive emulsion. As soon as the light sensitivea developer by which-development can be carried out under any desired source of light, and particularly also in daylight The-process consists essentially in adding an alkali to complex compounds of iron with polyvalent phenols such as potassium salt of tripyrocatechin ferric acid having'the following chemical formula:

for the manufacture of daylight developers for photographic plates and the like are primarily alkali salts of tripyrocatechinferric acid. In addition to the said'salts of' tripyrocatechin-ferric acid the salts of dipyrocatechin-ferric acid can also be used. as

' these violent salts can be easily converted by excess of alkali into the red salts of tripyrocatechin-ferric acid with the separation of ferric hydroxide. It has-been observed that such complex compounds when dissolved in water have a powerful reducing action on photographic plates, films, papers, and the ultra rapid plate, is placed after exposure like coated with an emulsion sensitive to light, after the addition of the alkali, so that these solutions are admirably suitable for use as photographic developers. As the complex iron phenol compounds are only slightly dissociated in aqueous solution, they cannot be used as developers without the addition of an alkali, and only excess of at kali makes a good developer from them.

For the satisfactory development of photographic plates and thelike even very dilute solutions in water ofthese complex compounds sufiice whenan alkali is present to secure good results. As underthese circumstances only a small percentage of dissosource of light, also particularlv by-dayli ght Under t-hes'e circumstances it is merely necessary that the plates or the'l ike be placed in the dark or in a red light in the i bath.

The re emulsion has been saturated with the developing solution, it has been rendered so thoroughly insensitive to light that the plates can be even repeatedly removed from the developer in any light, even daylight, in

order to observe the progress of the develop- 'ment.

After development has been completed,"

the plates are rinsed with water and can be fixed in an acid fixing bath in any li ht, even in" dayllght, without any further precautions havin to' be taken. The plates are following:-

2 grs. potassium salt of tripyrocatechin ferric acid, 198 com. distilled water, 15 com.

10% potassium hydroxide solution.

The plate to be developed, such as a Haufi' in the said develop r in a red lioht, after -which the electric Ii-g t can be switched on.

25 grs, sodium thio-sulphate. 3 grs. sodi- I um bi-sulphite, 72 ccm. distilled water. a

Plates developed by the above method have the disadvantage of showing a light brown to a reddish brown colour after fix ing. This is disadvantageous, as they :re-.

'quire a slightly longer time in copying for the production of positives. According to the present invention, this disadvantage is overcome by adding a water soluble sulphite to the daylight developer compounded according to the above process. This additlon of the water soluble sulphite completely overcomes the above mentioned disadvantage. The emulsion of the plate is, howeyer, normal in. every.re-

spect, as it copies in normalti'me, for exam?" ple. The process maybe illustrated by the following example To pre are the developer 2 grs. potassium salt of tripyroeatechin ferric acid and 5 grs.

sodium sulphite (crystalline) are dissolved in 200 ccm. distilled water, and ccm. of

a 10% solution of potassium hydroxide arc added.

The plates to be developed areplaced in the said developer in a red li 'ht, or in a darkv room, or under an absolutely lighttight cloth after exposure, after which theelectric light may be'switched on at once, .or da light admitted. After two minutes 'the p ate may be removed from the .de-

veloper repeatedly, both under a bright electric light, or even in daylight, in order to observe the progress of the development. After the p ate has been developed, it is rinsed oil with water, and fixed in a fixing bath of the following composition 25 grs. sodium thio-sulphate, 5 grs. sodium bi-sulphite, 70 com. distilled water, and then washed.

I claim 1. A developer for photographic plates, films, papers, and the like, prepared by makmg an aqueous solution of a, complex" salt of tripyrocatechin ferric acid, and adding alkali in excess thereto.

5. A developer for photographic plates, films, papers, and the like, prepared by forming an aqueous solution of potassium salt of tripyrocatechin ferric acid, andadding potassium hydroxide solution thereto.

6. A developer for films, papers and the like, prepared by disphotographic plates,

solving 2 grs. of potassium salt of tripyrocateclnn ferric acid in 198 ccni. of distilled water, and adding 15 com. 10% solution of potassium hydroxide thereto.

7. A process of developing a photographic plate, film, paper,- and the like, consisting in disposing t e exposed negative in a de; veloper prepared by dissolving 2 grs. of

otassium salt of trlpyrocatechin ferric acid 1n 198 com. of distilled water, and adding 15 ccm. 10% solution of' otassium hydroxide thereto, rinsin the eveloped negative and fixing ina batli prepared by dissolving 25 grs. of sodium thlo-sulphate and 3 grs. of sodium bisulphite in 72 com. of distilled water. I

' 8. A developer for photographic plates, films, papers, and the like, prepared by making an aqueous solution of a complex compound of iron with polyvalent. phenols, and adding an alkali and a water soluble sulphite theretovfor the purpose set forth.

9. A developer for photographic plates, films, papers, and the like prepared by making an aqueous solution of a complex compound of iron with polyvalent phenols,

and adding alkali in excess and a water soluble sulphite'thereto for the purpose set forth.

10. A developer for photographic plates, films, papers, and the .like, prepared by dissolving 2 grs. of potassium salt of tripyrocatechin ferric acid and 5 grs. of sodium sulphite (crystalline) in 200 com. of distilled water and adding 10 com. of a 10% solution of potassium h'ydroxide thereto.

' 11. -A process of developing a photographic plate, film, paper, orthe like, consistmg in disposing the expoted negative in a developer prepared by dissolving- 2 grs. of potassium sa t,of tripyrocatechin ferric acid and 5 grs. of sodium sulphite (crystalline) in 200 ccm. of distilled water, and add ing 10 com. of a 10% solution of potassium hydroxide thereto, rinsing the developed negative and fixing in a bath prepared by dissolving 25 grs. of sodium thio-sulphate and 5 of distilled water.

In testimony whereof I aflix mysignature.

4 KARL. BINDER.

s. of sodium bi-sulphite in 70,ccm.. 

